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At least 343 records · Page 19Linked to original sources
PubMed1998

Analysis of the in vivo nitrosation capacity of the larvae used in the wing somatic mutation and recombination test of Drosophila melanogaster.

The in vivo nitrosation capacity of third-instar larvae of Drosophila melanogaster was assessed using the wing somatic mutation and recombination test (SMART). Larvate derived from two different crosses, the standard cross (ST) and the high bioactivation cross (HB) both involving the recessive wing cell markers multiple wing hairs (mwh) and flare (flr3), were used. The HB cross is characterised by an increased cytochrome P450-dependent bioactivation capacity for promutagens and procarcinogens. The larvae were treated either with methyl urea, sodium nitrite or its combination. N-Nitrosomethylurea was used as a positive control. The wings of the resulting flies were analysed for the occurrence of mutant spots produced by various types of mutational events or by mitotic recombination. Methyl urea is negative in the ST and the HB cross, whereas sodium nitrite is weakly genotoxic in both crosses. However, the combination of both compounds produces highly increased frequencies of mutations and recombinations predominantly in the HB cross. The genotoxic effects produced by the combined treatments were considerably increased when mashed potatoes or an agar-yeast medium were used for the treatment instead of the standard instant medium. Treatment of larvae with the mixture resulting from the in vitro reaction of nitrosation precursors also resulted in high frequencies of induced spots comparable to those recorded with the potent genotoxin N-nitrosomethylurea. Further experiments showed that the genotoxic effect resulting from the in vivo exposure to nitrosation precursors can be reduced by co-treatment with catechin, a known nitrosation inhibitor. The present study demonstrates that the wing spot test is well suited for the determination of genotoxicity produced by in vivo nitrosation processes and for the study of their modulation by individual compounds or dietary complex mixtures.

Animals↗
PubMed1996

Specification of the wing by localized expression of wingless protein.

Limb development in Drosophila depends on subdivision of the limb primordia into functional units called compartments. Cell interactions across compartment boundaries establish pattern-organizing centres that control growth and specify cell fates along the anteroposterior (AP) and dorsoventral (DV) axes of the limbs. AP subdivision of the disc primordia is inherited from the embryonic ectoderm. DV subdivision of the wing disc occurs during the second larval instar through localized expression of the apterous protein (Apterous) in dorsal cells. A third major subdivision of the wing disc into wing and body-wall compartments also occurs in the second instar. Here we show that specification of the wing primordium in early second instar depends on activity of the AP patterning system but not the DV system. These results define two distinct roles for the wingless gene: a primary role in specifying the wing primordium, and a subsequent role mediating the patterning activities of the DV compartment boundary.

Animals↗
PubMed2003

Wingless promotes cell survival but constrains growth during Drosophila wing development.

During animal development, organs grow to a fixed size and shape. Organ development typically begins with a rapid growth phase followed by a gradual decline in growth rate as the organ matures, but the regulation of either stage of growth remains unclear. The Wnt/Wingless (Wg) proteins are critical for patterning most animal organs, have diverse effects on development and have been proposed to promote organ growth. Here we report that contrary to this view, Wg activity actually constrains wing growth during Drosophila melanogaster wing development. In addition, we demonstrate that Wg is required for wing cell survival, particularly during the rapid growth phase of wing development. We propose that the cell-survival- and growth-constraining activities of Wg function to sculpt and delimit final wing size as part of its overall patterning programme.

Animals↗
PubMed2001

The contrasting genetic architecture of wing size and shape in Drosophila melanogaster.

Surprisingly little is known about the genetic architecture of body size in natural populations of Drosophila melanogaster. Using both generation means and triple-test-cross analyses, we investigated the genetic architecture of wing size (an indicator of body size) and wing shape in a naturally occurring body size cline. For wing size, we found significant epistatic genetic variance and evidence of past directional selection for increased body size. While wing shape also exhibits significant epistatic genetic variance, there was no indication of directional selection, suggesting instead a history of optimizing selection. Our results support the idea that epistatic variance may be more common in natural populations than was once suspected. Also, our results suggest substantial directional selection on wing size but not shape.

Animals↗
PubMed1997

Color pattern formation on the wing of the butterfly Pieris rapae. 1. Cautery induced alteration of scale color and delay of arrangement formation.

Experimental approaches to color pattern formation of lepidopteran insects have been made exclusively by analyzing pattern alterations in adult wings induced by operations. We microcauterized the presumptive black region of the dorsal forewing of the butterfly Pieris rapae and analyzed not only the resultant color pattern in the adult wing but also the cell behavior in the pupal wing epidermis around the injury. Cautery induced color alterations were as follows: (i) cautery up to 49.5 h after pupation resulted in white regions appearing within the black region while later cauteries induced larger white regions; (ii) cautery between 50 and 59.5 h resulted in the white regions induced by the cauteries being dramatically decreased; (iii) cautery after 60 h resulted in white regions that had almost disappeared. The examination of the cell behavior in the pupal wing epidermis after cauteries showed that the row formation of scale precursor cells was delayed. This delayed area varied with the time of cautery, in the same manner as that in the induced white area in the adult wing ((i)-(iii) above). The relationship between scale color alteration and the developmental delay of the scale row formation is discussed.

Animals↗
PubMed1997

Color pattern formation on the wing of a butterfly Pieris rapae. 2. Color determination and scale development.

It has been shown that microcautery on the prospective apical black region of the early pupal forewing of a butterfly, Pieris rapae, causes alteration of the scale color on the adult wing and a delay in histogenesis of the pupal wing. From these results, it has been assumed that the developmental delay of scale cells in the pupal wing alters their developmental fate and the hypothesis that different color fates of scales are determined by differences in the developmental timetables between scale cells is proposed. In this study, we attempted to find the developmental timetables of individual scales expressing specific color to test this hypothesis. It was found that the holes on the upper surface of a scale become larger as they develop and the hole sizes of scales in the white region are always larger than in the black region on the same wings either during pupal period or after eclosion. This suggests that the scale hole size is a good index that reflects developmental rate of the scale and a difference in the hole size between adult scales is attributed to a difference in the developmental timetables when their ancestral scale precursor cells were in the pupal period. A comparison of the hole sizes between adult scales in different color regions suggested that normal white scales were in a more advanced state than were the black ones but white scales induced by microcautery were in a less advanced state than black ones on the same wing. This supports our hypothesis.

Animals↗
PubMed2000

Notch signaling directly controls cell proliferation in the Drosophila wing disc.

Notch signaling is involved in cell differentiation and patterning during morphogenesis. In the Drosophila wing, Notch activity regulates the expression of several genes at the dorsal/ventral boundary, and this is thought to elicit wing-cell proliferation. In this work, we show the effect of clones of cells expressing different forms of several members of the Notch signaling pathway, which result in an alteration of Notch activity. The ectopic expression in clones of activated forms of Notch or of its ligands (Delta or Serrate) in the wing causes outgrowths associated with the appearance of ectopic wing margins. These outgrowths consist of mutant territories and of surrounding wild-type cells. However, the ectopic expression of Delta, at low levels in ventral clones, causes large outgrowths that are associated neither with the generation of wing margin structures nor with the expression of genes characteristic of the dorsal/ventral boundary. These results suggest that Notch activity is directly involved in cell proliferation, independently of its role in the formation of the dorsal/ventral boundary. We propose that the nonautonomous effects (induction of extraproliferation and vein differentiation in the surrounding wild-type cells) result from pattern accommodation to positional values caused by the ectopic expression of Notch.

Alleles↗
PubMed2006

Development of bat flight: morphologic and molecular evolution of bat wing digits.

The earliest fossil bats resemble their modern counterparts in possessing greatly elongated digits to support the wing membrane, which is an anatomical hallmark of powered flight. To quantitatively confirm these similarities, we performed a morphometric analysis of wing bones from fossil and modern bats. We found that the lengths of the third, fourth, and fifth digits (the primary supportive elements of the wing) have remained constant relative to body size over the last 50 million years. This absence of transitional forms in the fossil record led us to look elsewhere to understand bat wing evolution. Investigating embryonic development, we found that the digits in bats (Carollia perspicillata) are initially similar in size to those of mice (Mus musculus) but that, subsequently, bat digits greatly lengthen. The developmental timing of the change in wing digit length points to a change in longitudinal cartilage growth, a process that depends on the relative proliferation and differentiation of chondrocytes. We found that bat forelimb digits exhibit relatively high rates of chondrocyte proliferation and differentiation. We show that bone morphogenetic protein 2 (Bmp2) can stimulate cartilage proliferation and differentiation and increase digit length in the bat embryonic forelimb. Also, we show that Bmp2 expression and Bmp signaling are increased in bat forelimb embryonic digits relative to mouse or bat hind limb digits. Together, our results suggest that an up-regulation of the Bmp pathway is one of the major factors in the developmental elongation of bat forelimb digits, and it is potentially a key mechanism in their evolutionary elongation as well.

Animals↗
PubMed1996

Cell cycling and patterned cell proliferation in the Drosophila wing during metamorphosis.

In metamorphosing wing discs, progression through the cell cycle takes place, as in larval discs, in nonclonally derived clusters of cells synchronized in the same cell cycle stage. Contrary to early discs, there are temporal and spatial heterogeneities in cell proliferation associated with wing margin, vein, intervein, and middle intervein territories. Within these territories, there are no indications of a wave progression of the cell cycle. Mitotic orientations are, as in early discs, at random but there is a preferential allocation of postmitotic cells along the proximodistal axis, thus explaining the elongated shape of the resulting clones along this axis. Shapes of clones in mature discs and in evaginated wings are similar, thus excluding major morphogenetic movements during evagination. After the proliferative period, all the cells are arrested in G1 phase. The final number of cells of the wing is fixed independently of experimental perturbations that alter the cell division schedule. These results are discussed in the context of a model of wing morphogenesis.

Animals↗
PubMed2003

Quantitative description and discrimination of butterfly wing patterns using moment invariant analysis.

Studies examining and using pattern variation in insects for identification and characterization of individuals and populations have been limited by the methods available for quantifying wing patterns objectively. In this paper, differences in wing pattern are demonstrated statistically using moment invariant data sets generated automatically from digitized images of the speckled wood butterfly, Pararge aegeria (Linnaeus). Studies with other biological subjects have already shown moment invariants to work well with outline shapes and silhouettes. A pilot study with replicated monochrome photographs of a single butterfly showed the method could detect pattern differences between wing surfaces, even in the presence of simulated wing fading and damage. In a further study of the wings of 228 specimens, multivariate analyses of variance using the moment data reliably detected differences between groups of butterflies according to sex, geographical origin and culture history. Potential applications and future improvements of the moment methodology are considered.

Analysis of Variance↗
PubMed1996

Wing morphometry of Phlebotomus perniciosus (Diptera:Psychodidae): calibration of methods with a laboratory population.

The wing morphometry of a laboratory-bred population of Phlebotomus perniciosus was studied using a semi-automatic, measurement system. The methods used were found to be precise, reproducible and valid for morphometrical studies. Each of several, different wing indices was found to be similar whether the wing was mounted in Hoyer's medium, Euparal or chloral balm. All samples showed similar differences between the wings of males and females, the wings of the males being smaller than those of the females.

Animals↗
PubMed1996

Roles for Rac1 and Cdc42 in planar polarization and hair outgrowth in the wing of Drosophila.

The wing of Drosophila melanogaster is covered by an array of distally pointing hairs. A hair begins as a single membrane outgrowth from each wing epithelial cell, and its distal orientation is determined by the restriction of outgrowth to a single distal site on the cell circumference (Wong, L., and P. Adler. 1993. J. Cell Biol. 123:209-211.). We have examined the roles of Cdc42 and Rac1 in the formation of wing hairs. We find that Cdc42 is required for localized actin polymerization in the extending hair. Interfering with Cdc42 activity by expression of a dominant negative protein abolishes both localized actin polymerization and hair outgrowth. In contrast, Rac1 is important for restricting the site at which hairs grow out. Cells expressing the dominant negative Rac1N17 fail to restrict outgrowth to a single site and give rise to multiple wing hairs. This polarity defect is associated with disturbances in the organization of junctional actin and also with disruption of an intricate microtubule network that is intimately associated with the junctional region. We also find that apical junctions and microtubules are involved in structural aspects of hair outgrowth. During hair formation, the apical microtubules that point distally elongate and fill the emerging wing hair. As the hair elongates, junctional proteins are reorganized on the proximal and distal edges of each cell.

Actin Cytoskeleton↗
PubMed1996

Genes regulating the remote wing margin enhancer in the Drosophila cut locus.

The mechanisms that allow enhancers to activate promoters from thousands of base pairs away are disrupted by the suppressor of Hairy-wing protein (SUHW) of Drosophila. SUHW binds a DNA sequence in the gypsy retrotransposon and prevents enhancers promoter-distal to a gypsy insertion in a gene from activating without affecting promoter-proximal enhancers. Several observations indicate that SUHW does not affect enhancer-binding activators. Instead, SUHW may interfere with factors that structurally facilitate interactions between an enhancer and promoter. To identify putative enhancer facilitators, a screen for mutations that reduce activity of the remote wing margin enhancer in the cut gene was performed. Mutations in scalloped, mastermind, and a previously unknown gene, Chip, were isolated. A TEA DNA-binding domain in the Scalloped protein binds the wing margin enhancer. Interactions between scalloped, mastermind and Chip mutations indicate that mastermind and Chip act synergistically with scalloped to regulate the wing margin enhancer. Chip is essential and also affects expression of a gypsy insertion in Ultrabithorax. Relative to mutations in scalloped or mastermind, a Chip mutation hypersensitizes the wing margin enhancer in cut to gypsy insertions. Therefore, Chip might encode a target of SUHW enhancer-blocking activity.

Animals↗
PubMed1997

Autosomal mutations affecting adhesion between wing surfaces in Drosophila melanogaster.

Integrins are evolutionarily conserved transmembrane alpha,beta heterodimeric receptors involved in cell-to-matrix and cell-to-cell adhesions. In Drosophila the position-specific (PS) integrins mediate the formation and maintenance of junctions between muscle and epidermis and between the two epidermal wing surfaces. Besides integrins, other proteins are implicated in integrin-dependent adhesion. In Drosophila, somatic clones of mutations in PS integrin genes disrupt adhesion between wing surfaces to produce wing blisters. To identify other genes whose products function in adhesion between wing surfaces, we conducted a screen for autosomal mutations that produce blisters in somatic wing clones. We isolated 76 independent mutations in 25 complementation groups, 15 of which contain more than one allele. Chromosomal sites were determined by deficiency mapping, and genetic interactions with mutations in the beta PS integrin gene myospheroid were investigated. Mutations in four known genes (blistered, Delta, dumpy and mastermind) were isolated. Mutations were isolated in three new genes (piopio, rhea and steamer duck) that affect myo-epidermal junctions or muscle function in embryos. Mutations in three other genes (kakapo, kiwi and moa) may also affect cell adhesion or muscle function at hatching. These new mutants provide valuable material for the study of integrin-dependent cell-to-cell adhesion.

Animals↗
PubMed1972

Developmental analysis of the wing disc in the mutant engrailed of Drosophila melanogaster.

The engrailed (en) mutation leads to the transformation of the posterior structures of the dorsal mesothoracic disc into those characteristic of the anterior region of the same disc. Similar posterior-anterior duplications have been detected in dorsal as well as ventral structures of all the thoracic segments. -Genetic combinations of en with other pattern mutants have shown their synergistic effect on the posterior wing pattern.-A clonal analysis of the en wing disc shows that en affects its development in a characteristic way. The genetic change, by induced mitotic recombination, of en(+) into en cells is followed by the corresponding transformation, except when it takes place some cell divisions prior to differentiation.-The en posterior wing disc cells show positive affinities with normal anterior wing disc cells in aggregates.-The mode of action of the en(+) locus controlling wing disc development is discussed.

Age Factors↗
PubMed1972

A study of the genetic basis of the sexual dimorphism for wing length in Drosophila melanogaster.

The genetic basis of a sexually dimorphic quantitative character in Drosophila melanogaster was investigated by means of two-way directional selection for increased and decreased differences between male and female wing length. The sex dimorphism (SD), defined as the mean wing length difference between the sexes, within families, provided the criterion for selection.-The two lines (High SD, Low SD) diverged rapidly during the 15 generations of selection, indicating the presence of extensive genetic variability for the genotype-sex interaction underlying the observed sexual dimorphism. There was evidence that genetic variability persisted in both lines when selection was relaxed. Most of the divergence between the two lines remained after 10 generations of relaxed selection.-The change in the level of sex dimorphism in the High line was due primarily to a decrease in male wing length; in the Low line most of the change in SD was the result of a decrease in female wing length. An overall reduction in wing length in both sexes in both lines is interpreted as an effect of inbreeding.-The distribution and nature of the genetic control underlying the SD characteristic of the two selection lines was investigated by chromosome substitution between selection lines using a marked inversion technique. The two lines differed by factors located on each of the three major chromosome pairs. Chromosome III had the greatest effect on the difference in SD level between lines, and showed an overall additive effect when present in homozygous versus heterozygous combination. Chromosome II had the least effect, with a significant dominance effect of the High II being evident when heterozygotes were compared with homozygotes. The effect of the X chromosome was intermediate. There was some evidence of interaction between non-homologous chromosomes.

Analysis of Variance↗
PubMed2001

Recombinagenic activity of four compounds in the standard and high bioactivation crosses of Drosophila melanogaster in the wing spot test.

The wing somatic mutation and recombination test (SMART) using Drosophila melanogaster was employed to determine the recombinagenic and mutagenic activity of four chemicals in an in vivo eukaryotic system. Two different crosses involving the wing cell markers mwh and flr(3) were used: the standard cross and a high bioactivation cross. The high bioactivation cross is characterized by a high constitutive level of cytochromes P450 which leads to an increased sensitivity to a number of promutagens and procarcinogens. Three-day-old larvae derived from both crosses were treated chronically with the oxidizing agent potassium chromate and with the three procarcinogens cyclophosphamide, p-dimethylaminoazobenzene and 9,10-dimethylanthracene. From both crosses two types of progeny were obtained: marker-heterozygous and balancer-heterozygous. The wings of both genotypes were analysed for the occurrence of single and twin spots expressing the mwh and/or flr(3) mutant phenotypes. In the marker-heterozygous genotype the spots can be due either to mitotic recombination or to mutation. In contrast, in the balancer-heterozygous genotype only mutational events lead to spot formation, all recombination events being eliminated. The oxidizing agent potassium chromate was equally and highly genotoxic in both crosses. Surprisingly, the promutagen cyclophosphamide also showed equal genotoxicity in both crosses, whereas p-dimethylaminoazobenzene was negative in the standard cross, but clearly genotoxic in the high bioactivation cross. 9,10-Dimethylanthracene showed a rather weak genotoxicity in the high bioactivation cross. Analyses of the dose-response relationships for mwh clones recorded in the two wing genotypes demonstrated that all four compounds are recombinagenic. The fraction of all genotoxic events which are due to mitotic recombination ranged from 83% (9,10-dimethylanthracene) to 99% (p-dimethylaminoazobenzene). These results demonstrate that the wing spot test in Drosophila is most suited to the detection of recombinagenic activity of genotoxic chemicals.

Animals↗
PubMed2004

Genotoxicity of tamoxifen citrate and 4-nitroquinoline-1-oxide in the wing spot test of Drosophila melanogaster.

Tamoxifen (TAM) is an anti-oestrogen used for treatment and prevention of human breast cancer, but it is also related to human endometrial and uterine cancer. The wing spot test in Drosophila melanogaster was employed to determine the genotoxic effects of TAM and 4-nitroquinoline-1-oxide (4-NQO), a carcinogen that produces adducts similar to TAM-DNA adducts detected in rodent liver and human liver microsomes. As Drosophila spp. have no oestrogen receptor, no effects can result in binding of TAM to a receptor. Chronic treatments with TAM citrate were performed with 3-day-old larvae of the standard (ST) and high bioactivation (HB) crosses of the wing spot test at concentrations of 0.66, 1.66 and 3.33 mM. In addition, the carcinogen 4-NQO was administered at 2.5 and 5.0 mM. Somatic spots on normal wings from marker-heterozygous flies and on serrate wings from balancer-heterozygous flies were scored to determine mutation and recombination events in somatic cells for each compound. The results showed genotoxic effects of TAM at 1.66 and 3.33 mM in the ST cross only and without a clear dose-response effect. This suggests a weak genotoxicity of this anti-oestrogen. The negative results obtained with TAM in the HB cross may indicate efficient detoxification of the compound by the increased xenobiotic metabolism present in this cross. As reported before, 4-NQO showed genotoxic effects in the ST cross with a clear dose-response effect. For the first time, we report enhanced effects of this compound in the HB cross. It is concluded that the genotoxicity of TAM in the Drosophila wing spot test is different from that of 4-NQO.

4-Nitroquinoline-1-oxide↗